In the single acting hydraulic cylinder, an internal space of a cylinder tube is partitioned to a rod side chamber and an anti-rod side chamber by a piston. The anti-rod chamber is connected to a hydraulic source through a feed/discharge port formed at a bottom of the cylinder tube. The piston is slidably supported with respect to the cylinder tube by a bearing provided on an outer periphery of the piston.
JP2000-170711A discloses a single acting hydraulic cylinder including a check valve mechanism for discharging an operating liquid leaking out from the anti-rod side chamber to the rod side chamber to the anti-rod side chamber. This check valve mechanism is constituted by a U-ring serving as a seal provided on an outer periphery of the piston and a through hole provided in the piston.
The U-ring is disposed with a lip directed toward the anti-rod side chamber side. The through hole is faced with the U-ring and is opened in the anti-rod side chamber. When a pressure in the rod side chamber is higher than a pressure in the anti-rod side chamber, the U-ring is crushed. As a result, the operating liquid in the rod side chamber is discharged to the anti-rod side chamber through the outer periphery of the U-ring and the through hole.